fix(contract): eventIterator should cleanup on validation failure (#715)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Bug Fixes**
* Improved cleanup handling for async generators when errors occur
during value mapping or validation, ensuring proper cancellation and
resource release.

* **Tests**
* Added test cases to verify that cleanup logic runs correctly when
errors are thrown in value mapping or when validation fails in async
generators.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: dinwwwh

packages/client/src/event-iterator.test.ts

@@ -155,4 +155,35 @@ describe('mapEventIterator', () => {
     await expect(mapped.throw(new Error('TEST'))).rejects.toThrow()
     expect(finished).toBe(true)
   })
+
+  it('cancel original when error is thrown in value map', async () => {
+    let finished = false
+
+    const iterator = (async function* () {
+      try {
+        yield 1
+        yield 2
+      }
+      finally {
+        finished = true
+      }
+    })()
+
+    const map = vi.fn(async (v) => {
+      if (v === 2) {
+        throw new Error('TEST')
+      }
+      return { mapped: v }
+    })
+
+    const mapped = mapEventIterator(iterator, {
+      value: map,
+      error: async error => error,
+    })
+
+    await expect(mapped.next()).resolves.toEqual({ done: false, value: { mapped: 1 } })
+    await expect(mapped.next()).rejects.toThrow('TEST')
+
+    expect(finished).toBe(true)
+  })
 })

packages/client/src/event-iterator.ts

@@ -35,9 +35,7 @@ export function mapEventIterator<TYield, TReturn, TNext, TMap = TYield | TReturn
 
       throw mappedError
     }
-  }, async (reason) => {
-    if (reason !== 'next') {
-      await iterator.return?.()
-    }
+  }, async () => {
+    await iterator.return?.()
   })
 }

packages/contract/src/event-iterator.test.ts

@@ -88,6 +88,26 @@ describe('eventIterator', async () => {
       return true
     })
   })
+
+  it('cleanup origin when validation fails', async () => {
+    let cleanupCalled = false
+    const schema = eventIterator(z.object({ order: z.number() }))
+
+    const result = await schema['~standard'].validate((async function* () {
+      try {
+        yield { order: 1 }
+        yield { order: '2' }
+        yield { order: 3 }
+      }
+      finally {
+        cleanupCalled = true
+      }
+    })())
+
+    await expect((result as any).value.next()).resolves.toEqual({ done: false, value: { order: 1 } })
+    await expect((result as any).value.next()).rejects.toThrow('Event iterator validation failed')
+    expect(cleanupCalled).toBe(true)
+  })
 })
 
 it('getEventIteratorSchemaDetails', async () => {